1. Field of the Invention
The present invention relates to a motor device having a motor and a rotation speed reduction mechanism for driving a wind shield wiper with a construction that the motor device is easily fixed to a wiper frame.
2. Description of Related Art
In a conventional motor device having a gear housing in which a reduction mechanism for reducing a rotation speed of a motor is housed, the gear housing is generally made through forming processing such as aluminum die-casting or resin molding. As it is necessary to form a shaft hole by which an output shaft of the reduction mechanism is held so as to penetrate through the gear housing, the gear housing is formed preferably in a manner that dies to be used for the forming processing may be parted in an axial direction of the output shaft thereof.
On the other hand, as shown in FIG. 9, the gear housing 100 is provided with installation legs 104 for fixing the motor device. The installation legs 104 are fixed to a flat surface portion 102A of a frame 102 having a one side open square shaped cross section. Each of the installation legs 104 is provided with a through hole 108 into which a bolt 106 is inserted on fixing to the frame 102. The through hole 108 is formed to extend in a direction same as the direction in which the dies are parted in view of easily splitting out the dies after forming. When the gear housing 100 is fixed to the flat surface portion 102A of the frame 102 by the bolt 106 and a nut 110, it is preferable, as shown in FIG. 10, that the flat surface portion 102A is faced in parallel with the output shaft of the reduction mechanism in consideration of a strength of the frame 120 for supporting the wiper device.
In the case that the gear housing 100 is fixed to the flat surface portion 102A faced in parallel with the output shaft of the reduction mechanism, the gear housing 100 may be provided, as shown in JP-U-5-40063, separately with a bracket made by press forming a plate in a given shape. However, this causes a problem that more manufacturing time and component parts are required, resulting in more manufacturing cost.
Further, to solve the above problem, if the gear housing 100 is provided integrally with installation legs 114 having through holes 112 extending perpendicularly to the output shaft of the gear housing 100, as shown in FIG. 10, the through holes 112 may not be formed in the gear housing 100 simply by upper and lower dies. In this case, a moving core in the dies becomes necessary for forming the through holes 112 so that the construction of the dies becomes complicated.
Further, as a process for fixing the gear housing 100 to the frame 102, at first, while the nut 110 is held in one hand, the bolt 106 have to be inserted into the through hole 112 and be tentatively screwed into the nut 110. Then, the bolt 106 is rigidly fastened with the nut 110 by a fastening tool. As a result, not only the fastening process becomes troublesome but also the nut 110 is likely to fall down during the fixing work.
The present invention has been made in view of the above mentioned problem, and an object of the present invention is to provide a motor device having a reduction mechanism in which an installation leg with a through hole formed nearly perpendicularly to an axis of an output shaft of the reduction mechanism is integrally formed with a gear housing without using a special moving core. As a result, while the manufacturing cost becomes less, a work for fixing the gear housing to a frame becomes easier.
To achieve the above object, the motor device is comprised of a motor, a reduction mechanism having an output shaft and a housing with an installation portion for housing the reduction mechanism so as to have the output shaft penetrate therethrough. The housing is formed integrally with the installation portion by a pair of dies parting in an axial direction of the output shaft.
The installation portion is composed of a side surface coming in surface contact with a seat surface of the frame, a first recess portion for holding a nut whose entire inner surface is opened at least on one side of the housing in the axial direction of the output shaft and a second recess portion for inserting a bolt whose entire inner surface is opened on the other side of the housing in the axial direction of the output shaft and which extends from the side surface to the first recess portion nearly perpendicularly to the axial direction of the output shaft.
According to the construction mentioned above, since the inner surfaces of the first and second recess portions are opened in a parting direction of the dies, respectively, for example, since the first recess portion may be formed by an upper die and the second recess portion may be formed by a lower dies, a through hole extending nearly perpendicularly to the parting direction of the dies may be formed as the second recess portion between the first recess portion and the frame. Therefore, the housing may be fixed to the frame by inserting the bolt through a penetrating hole of the frame into the second recess portion and screwing the bolt into the nut housed in the first recess portion.
As mentioned above, even if the second recess portion constituting the through hole is shaped nearly perpendicular to the axial direction of the output shaft, the through hole may be formed merely by the upper and lower dies without using a moving core. As a result, the housing may be easily manufactured at lower cost.
Preferably, the inner surface has a nut holding surface opened only on the one side of the housing in an opposing direction to a gravity so that, just by dropping the nut into the first recess portion, the nut may be housed in the first recess portion with its own weight. This makes the fastening work easier.
Further, it is preferable that the inner surface of the first recess portion has a retaining surface coming in contact with an outer surface of the nut and preventing the nut from rotating together with the bolt when the bolt is screwed into the nut. This construction serves to fix easily the housing to the frame without holding the nut in one hand.
Furthermore, preferably, the first recess portion is provided at the inner surface on a side opposite to the second recess portion with a concave portion at which a leading end of the bolt is housed when the bolt is fastened to penetrate through the nut. With the concave portion, the bolt may be further screwed into the nut even after the leading end of the bolt penetrates through the nut. As a result, the motor device may be reliably fixed to the frame irreverent to a length of the bolt.